Sheet conveying roller and production method therefor

ABSTRACT

The present invention provides a sheet conveying roller, which effectively reduces the amount of paper dust accumulated on its outer peripheral surface to thereby suppress sheet transportation failure. The sheet conveying roller includes a nonporous tubular elastic member ( 1 ). The elastic member ( 1 ) has a plurality of recesses ( 6 ) or a plurality of through-holes ( 8 ) equidistantly arranged in a center axis (L 1 ) direction thereof and equidistantly arranged in a circumferential direction thereof, and each having an opening having a round plan shape in an outer peripheral surface ( 2 ) thereof, wherein the recesses ( 6 ) each have a constant depth as measured thicknesswise of the elastic member ( 1 ), wherein the through-holes ( 8 ) each extend thicknesswise through the elastic member ( 1 ). A production method includes forming the elastic member by vulcanizing a rubber composition in a vulcanization mold having projections corresponding to the recesses or the through-holes.

TECHNICAL FIELD

The present invention relates to a sheet conveying roller to be used forconveying sheets in electrostatic copying machines, various types ofprinters and the like, and to a production method for the sheetconveying roller.

BACKGROUND ART

Various types of sheet conveying rollers are incorporated in sheetconveying mechanisms provided, for example, in electrostatic copyingmachines, laser printers, plain paper facsimile machines,copier-printer-facsimile multifunction machines, inkjet printers,automatic teller machines (ATM) and the like.

Examples of the sheet conveying rollers include sheet feed rollers,transport rollers, platen rollers and sheet output rollers, which areeach adapted to be rotated in frictional contact with a sheet (the term“sheet” is herein defined to include a paper sheet, a plastic film andthe like, and this definition is effective in the following description)to convey the sheet.

Such a conventional sheet conveying roller typically includes a tubularelastic member made of a rubber such as a natural rubber (NR), aurethane rubber (U), an ethylene-propylene-diene rubber (EPDM), apolynorbornene rubber, a silicone rubber or a chlorinated polyethylenerubber, and having an outer peripheral surface serving as a contactsurface to be brought into contact with the sheet.

However, paper dust and dirt generated from paper sheets are liable toadhere to the outer peripheral surface of the elastic member. As thesheet conveying roller is repeatedly brought into contact with the papersheets, the paper dust and the dirt are accumulated on the outerperipheral surface. This reduces the contact area and the frictionalcoefficient of the elastic member with respect to a paper sheet, therebycausing sheet transportation failure at a relatively early stage.

Particularly, paper sheets having a higher ash content are widely usedfor reduction of running costs of the machines in recent years. Thehigher ash content paper sheets are more liable to generate paper dustand dirt, so that the accumulation of the paper dust and the dirt andthe sheet transportation failure attributable to the accumulation aremore liable to occur.

Various attempts have been made to prevent the accumulation of the paperdust and the dirt, and the sheet transportation failure attributable tothe accumulation.

Patent Literature 1, for example, discloses a so-called knurled roller,which includes a non-porous tubular elastic member such as of a rubberhaving a plurality of grooves formed in an outer peripheral surfacethereof as extending parallel to its axis along its entire width for useas a sheet conveying roller.

The grooves of the knurled roller function as pockets for trapping paperdust and dirt, thereby reducing the amount of the paper dust and thedirt accumulated on the outer peripheral surface to be brought intodirect contact with paper sheets. Thus, the sheet transportation failurecan be suppressed which may otherwise occur due to the accumulation ofthe paper dust and the dirt.

However, the knurled roller suffers from the following problem, becausethe grooves extend axially of the elastic member along the entire widthof the elastic member.

Consider a state in which a region of the outer peripheral surface ofthe elastic member formed with the groove is in contact with a sheet anda state in which a region of the outer peripheral surface of the elasticmember formed with no groove is in contact with a sheet. A sheet contactarea is smaller in the former state than in the latter state and, hence,a sheet transportation force is smaller in the former state than in thelatter state.

Therefore, the two types of regions having different transportationforces are alternately brought into contact with the sheet, as theknurled roller is rotated. Accordingly, the sheet transportation forceis pulsated. This makes it impossible to maintain the transportationforce at a constant level.

Consider a state in which opposite edges of the groove abut against thesheet. In this state, a distance between the center axis of the knurledroller and the sheet is smaller than in the state in which the region ofthe outer peripheral surface formed with no groove abuts against thesheet. That is, the knurled roller virtually has different outerdiameters in the region thereof formed with the groove and in the regionthereof formed with no groove.

Therefore, the two types of regions having different outer diameters arealternately brought into contact with the sheet, as the knurled rolleris rotated. Accordingly, the sheet transportation speed is alsopulsated. This makes it impossible to maintain the transportation speedat a constant level.

Further, the region of the outer peripheral surface formed with nogroove transports the sheet in surface contact with the sheet, while theregion of the outer peripheral surface formed with the groove transportsthe sheet with the edges of the groove brought into line contact withthe sheet by a so-called scratching effect. Where paper sheets having agreater amount of paper dust and dirt are occasionally transported, forexample, the grooves extending along the entire width of the knurledroller simultaneously lose the scratching effect along their entirelengths, so that the sheets are liable to suffer from slippage.

Therefore, the knurled roller liable to suffer from the pulsation of thetransportation speed and the slippage is not suitable for a useapplication requiring precise sheet feeding or for a use applicationrequiring the control of the sheet feed amount for the sheet feeding.

In addition, a sheet contact pressure does not act on a groove portionof the knurled roller and, if the sheet contact pressure is set at ahigher level, there is a great difference in contact pressure betweenthe groove portion and portions of the knurled roller located atopposite sides of the groove portion, resulting in wrinkle orindentation of the sheet.

Patent Literature 2 discloses a sheet conveying roller including aporous elastic member produced as having a multiplicity of cells byvulcanizing and foaming a rubber composition containing a foaming agent,and grinding an outer peripheral surface of the elastic member to exposemultiple cells adjacent to the outer peripheral surface to formopenings.

In the sheet conveying roller, the openings function as pockets fortrapping paper dust and dirt, thereby reducing the amount of the paperdust and the dirt accumulated on the outer peripheral surface to bebrought into direct contact with the paper sheet. Thus, the sheettransportation failure attributable to the accumulation of the paperdust and the dirt can be suppressed.

However, the porous elastic member has a smaller density, and is liableto be worn or suffer from a so-called permanent compressive deformationwhich is a phenomenon such that the elastic member is not restored toits original diameter after being compressed for a long period of time.Therefore, the sheet conveying roller including the porous elasticmember is more liable to suffer from the wear and the permanentcompressive deformation and, hence, has a shorter product service lifethan a sheet conveying roller including a non-porous elastic member.

If the outer diameter of the sheet conveying roller is changed due tothe wear or the permanent compressive deformation, the sheet feed amountis significantly reduced as compared with the initial state even if thesheet conveying roller is rotated at the same rotation speed. That is,the sheet feed amount is not constant, but constantly changed due to thewear and the permanent compressive deformation of the elastic member.

Therefore, the sheet conveying roller including the porous elasticmember is not suitable for a use application requiring precise sheetfeeding or for a use application requiring the control of the sheet feedamount for the sheet feeding.

The shapes, the dimensions and the density (the per-unit-area number) ofand distances between the openings formed in the outer peripheralsurface, for example, by the foaming of the foaming agent and thesubsequent grinding are not uniform, but vary on the outer peripheralsurface of the elastic member. If the number of the openings is locallyreduced or the diameters of the individual openings are locally reducedin some region on the outer peripheral surface, for example, theopenings in the region fail to sufficiently function as the pockets fortrapping the paper dust and the dirt, thereby failing to sufficientlysuppress the sheet transportation failure attributable to theaccumulation of the paper dust and the dirt. The variation in thegeometry of the openings varies from product to product, so that thesheet transportation failure suppressing function also varies fromproduct to product.

Patent Literature 3 discloses an elastic member which includes aplurality of annular grooves provided in an outer peripheral surfacethereof and arranged perpendicularly to the axis thereof as extendingcircumferentially of the outer peripheral surface.

However, the grooves extending circumferentially of the outer peripheralsurface fail to sufficiently function as pockets for trapping paper dustand dirt as compared with the aforementioned axial grooves and theopenings of the porous cells.

In the two types of sheet conveying rollers previously described, thepaper dust and the dirt adhering to the outer peripheral surface of theelastic member are conveyed to the axial grooves or the openings of theporous cells by the rotational force applied mainly circumferentially ofthe outer peripheral surface, and trapped in the axial grooves or theopenings of the porous cells.

However, the circumferential grooves extend generally parallel to thedirection of the rotational force, thereby failing to efficiently conveyand trap the paper dust and the dirt by the rotational force.

Therefore, the circumferential grooves fail to sufficiently function asthe pockets for trapping the paper dust and the dirt.

In addition, a sheet contact pressure does not act on a groove portionof the sheet conveying roller and, if the sheet contact pressure is setat a higher level, there is a great difference in contact pressurebetween the groove portion and portions of the sheet conveying rollerlocated at opposite sides of the groove portion, resulting in wrinkleand indentation of the sheet.

CITATION LIST Patent Literature

-   [Patent Literature 1] JP-HEI10 (1998)-59578A-   [Patent Literature 2] JP-2002-46873A-   [Patent Literature 3] JP-2000-118779A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

It is an object of the present invention to provide a sheet conveyingroller, which effectively reduces the amount of paper dust and dirtaccumulated on its outer peripheral surface to thereby suppress thesheet transportation failure, and is less liable to suffer from theslippage with the sheet transportation force and the sheettransportation speed thereof kept constant throughout the entirecircumference thereof even if paper sheets having a greater amount ofpaper dust and dirt are occasionally transported, and is less liable tosuffer from the change in the outer diameter thereof due to wear andpermanent compressive deformation to thereby substantially prevent thesheet from being wrinkled or indented even if the contact pressure isset at a higher level. It is another object of the present invention toprovide a production method which permits efficient production of theinventive sheet conveying roller at higher productivity.

Solution to Problem

The present invention provides a sheet conveying roller, which includesa non-porous tubular elastic member, wherein the elastic member has aplurality of recesses or a plurality of through-holes provided in anouter peripheral surface thereof as equidistantly arranged in a centeraxis direction thereof and equidistantly arranged in a circumferentialdirection thereof, and each having an opening having a round plan shapeor a plan shape inscribed inside a circle in the outer peripheralsurface thereof, wherein the recesses each have a constant depth asmeasured thicknesswise of the elastic member, wherein the through-holeseach extend thicknesswise through the elastic member.

According to the present invention, the elastic member is non-porousand, therefore, is less liable to suffer from the change in the outerdiameter thereof due to the wear and the permanent compressivedeformation than the porous elastic member, thereby having a prolongedproduct service life. Further, the sheet feed amount is prevented frombeing changed due to the change in the outer diameter, and is constantlymaintained at a certain level.

According to the present invention, the recesses or the through-holeseach having the opening having the round plan shape or the plan shapeinscribed inside the circle are provided in the outer peripheral surfaceof the elastic member as equidistantly arranged in the center axisdirection of the elastic member and equidistantly arranged in thecircumferential direction of the elastic member.

Therefore, the recesses or the through-holes efficiently and uniformlyfunction as pockets for trapping the paper dust and the dirt over theentire outer peripheral surface, thereby reducing the amount of thepaper dust and the dirt accumulated on the outer peripheral surface tobe brought into direct contact with the paper sheet. Thus, the sheettransportation failure can be suppressed which may otherwise occur dueto the accumulation of the paper dust and the dirt. A distance betweenthe recesses or the through-holes in the axially equidistant arrangementand a distance between the recesses or the through-holes in thecircumferentially equidistant arrangement may be the same or different.

The openings of the recesses or the through-holes are evenly present inthe entire outer peripheral surface of the tubular elastic member and,unlike the grooves in the prior art rollers, eliminate the possibilitythat the outer peripheral surface of the elastic member iscircumferentially discontinuous. Therefore, the outer dimensions of theentire outer peripheral surface of the elastic member are constant.Thus, the sheet transportation speed at which the sheet is conveyed bythe rotation of the sheet conveying roller can be constantly maintainedat a certain level.

In addition, the openings of the recesses or the through-holes areequidistantly arranged in the axial direction of the elastic member andequidistantly arranged in the circumferential direction of the elasticmember, so that the sheet contact area of the outer peripheral surfacehaving the openings of the recesses or the through-holes is generallyconstant over the entire outer peripheral surface. Thus, the sheettransportation force with which the sheet is conveyed by the rotation ofthe sheet conveying roller can be constantly maintained at a certainlevel.

As a result, the sheet slippage can be reliably prevented even if papersheets having a greater amount of paper dust and dirt are occasionallytransported.

Therefore, the inventive sheet conveying roller is less liable to sufferfrom the change in the outer diameter thereof due to the wear or thepermanent compressive deformation of the elastic member as describedabove. In addition, the inventive sheet conveying roller can beadvantageously used for the application requiring the precise sheetfeeding or for the application requiring the control of the sheet feedamount for the sheet feeding.

In addition, the sheet conveying roller holds the sheet while the entireperipheries of some of the openings in the outer peripheral surface ofthe elastic member are kept in press contact with the sheet. Further,the openings each have a significantly smaller size than the axialgrooves or the circumferential grooves in the prior art rollers.Therefore, even if the contact pressure is set at a higher level, forexample, the sheet is prevented from being wrinkled or indented.

The plan shapes of the recesses or the through-holes preferably includeat least one shape selected from the group consisting of a round shape,a rectangular shape, a rhombic shape, an oval shape, a five or moresided polygonal shape and a combination of any of these shapes.

The present invention provides a method of producing a sheet conveyingroller, the method comprising the steps of:

providing a vulcanization mold which includes an outer mold and an innermold,

the outer mold being circumferentially dividable into at least two moldpieces, and having a shape-imparting tubular inner surface correspondingto an outer peripheral surface of an elastic member of the sheetconveying roller, and a plurality of projections projecting radiallyinward from the shape-imparting inner surface and each having asectional shape corresponding to a plan shape of recesses of the elasticmember and a projection height corresponding to a depth of the recessesas measured thicknesswise of the elastic member,

the inner mold having a shape-imparting tubular outer surface to belocated coaxially with the shape-imparting inner surface so as to bespaced a distance corresponding to the thickness of the elastic memberfrom the shape-imparting inner surface; and

forming the elastic member having the plurality of recessescorresponding to the projections in the outer peripheral surface thereofby preheating the vulcanization mold, locating the shape-imparting innersurface of the outer mold and the shape-imparting outer surface of theinner mold of the vulcanization mold coaxially with each other, fillinga space defined between the shape-imparting inner surface and theshape-imparting outer surface with a rubber composition as a materialfor the elastic member, and vulcanizing the rubber composition.

According to the present invention, the inventive sheet conveying rollerincluding the elastic member having the plurality of recesses can beefficiently produced at higher productivity.

The present invention further provides a method of producing a sheetconveying roller, the method comprising the steps of:

(1) providing a vulcanization mold which includes an outer mold and aninner mold,

the outer mold being circumferentially dividable into at least two moldpieces, and having a shape-imparting tubular inner surface having aninner diameter equal to a sum of an outer diameter of an elastic memberof the sheet conveying roller and a predetermined grinding margin,

the inner mold having a shape-imparting tubular outer surface to belocated coaxially with the shape-imparting inner surface so as to bespaced a distance equal to a sum of a thickness of the elastic memberand the grinding margin from the shape-imparting inner surface, and aplurality of projections projecting radially outward from theshape-imparting outer surface and each having a sectional shapecorresponding to a plan shape of through-holes of the elastic member anda projection height that is not less than the thickness of the elasticmember and less than the sum of the thickness of the elastic member andthe grinding margin, and

forming an elastic body having a plurality of recesses corresponding tothe projections in an inner peripheral surface of the elastic body bypreheating the vulcanization mold, locating the shape-imparting innersurface of the outer mold and the shape-imparting outer surface of theinner mold of the vulcanization mold coaxially with each other, fillinga space defined between the shape-imparting inner surface and theshape-imparting outer surface with a rubber composition as a materialfor the elastic member, and vulcanizing the rubber composition; and

(2) grinding an outer peripheral portion of the elastic body by thegrinding margin to expose the recesses in an outer peripheral surface ofthe resulting elastic body to form the plurality of through-holes in theelastic member.

According to the present invention, the inventive sheet conveying rollerincluding the elastic member having the plurality of through-holes canbe efficiently produced at higher productivity.

Effects of the Invention

According to the present invention, the sheet conveying roller isprovided, which effectively reduces the amount of paper dust and dirtaccumulated on its outer peripheral surface to thereby suppress thesheet transportation failure, and is less liable to suffer from theslippage with the sheet transportation force and the transportationspeed thereof kept constant throughout the entire circumference thereofeven if paper sheets having a greater amount of paper dust and dirt areoccasionally transported, and is less liable to suffer from the changein the outer diameter thereof due to the wear and the permanentcompressive deformation to thereby substantially prevent the sheet frombeing wrinkled or indented even if the contact pressure is set at ahigher level. According to the present invention, the production methodsare provided, which permit efficient production of the inventive sheetconveying roller at higher productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the appearance of an elastic memberwhich is a major portion of a sheet conveying roller according to oneembodiment of the present invention.

FIG. 2 is a sectional view illustrating a part of the elastic member ofFIG. 1 taken perpendicularly to a center axis L1 of FIG. 1 on anenlarged scale.

FIG. 3 is a sectional view illustrating a part of a modification of theelastic member taken perpendicularly to the center axis L1 of FIG. 1 onan enlarged scale.

FIGS. 4A to 4H are plan views showing exemplary plan shapes of athrough-hole or a recess having an opening in an outer peripheralsurface of the elastic member as seen perpendicularly to the outerperipheral surface.

FIG. 5 is a sectional view illustrating an exemplary vulcanization moldto be used for forming an elastic member having a plurality of recessesin an inventive production method.

FIG. 6 is a sectional view illustrating an exemplary vulcanization moldto be used for forming an elastic member having a plurality ofthrough-holes in another inventive production method.

EMBODIMENTS OF THE INVENTION

FIG. 1 is a perspective view showing the appearance of an elastic memberwhich is a major portion of a sheet conveying roller according to oneembodiment of the present invention. FIG. 2 is a sectional viewillustrating a part of the elastic member taken perpendicularly to acenter axis L1 of FIG. 1 on an enlarged scale. FIG. 3 is a sectionalview illustrating a part of a modification of the elastic member takenperpendicularly to the center axis L1 of FIG. 1 on an enlarged scale.FIG. 4A is a plan view showing an exemplary plan shape of a through-holeor a recess having an opening in an outer peripheral surface of theelastic member as seen perpendicularly to the outer peripheral surface.

Referring to FIG. 1, the elastic member 1 according to the embodimenthas a tubular shape having a constant thickness. The elastic member is anon-porous elastic member made of a natural rubber (NR), a urethanerubber (U), an ethylene propylene diene rubber (EPDM), a polynorbornenerubber, a silicone rubber or a chlorinated polyethylene rubber as in theprior art and containing substantially no air bubble therein.

The elastic member 1 has an outer peripheral surface 2 to be broughtinto direct contact with a sheet, and an inner peripheral surface 3. Theouter peripheral surface 2 and the inner peripheral surface 3 aredisposed coaxially with each other about the common center axis L1.Thus, the thickness of the elastic member 1 is constant throughout theentire circumference of the elastic member 1.

A sleeve not shown is fitted in the tubular elastic member 1 with anouter peripheral surface thereof fixed to the inner peripheral surface 3of the elastic member 1 directly or with an adhesive agent to providethe sheet conveying roller.

Opposite end faces 4, 5 of the elastic member 1 with respect to thecenter axis L1 are flat surfaces perpendicular to the center axis L1 andparallel to each other. Thus, the outer peripheral surface 2 of theelastic member 1 has a constant width throughout the entirecircumference thereof.

Referring to FIGS. 1 to 4( a), the elastic member 1 has a plurality ofrecesses 6 each having a predetermined depth D as measured along thethickness of the elastic member 1 or a plurality of through-holes 8 eachextending from the outer peripheral surface 2 to the inner peripheralsurface 3 of the elastic member 1. The recesses 6 or the through-holes 8each have an opening having a round plan shape in the outer peripheralsurface 2 of the elastic member 1 as seen perpendicularly to the outerperipheral surface.

Referring to FIGS. 1, 2 and 4(a), the recesses 6 each have a bottomsurface 7 having a round plan shape having the same diameter as theopening as seen perpendicularly to the outer peripheral surface 2. Aportion of each of the recesses 6 between the opening and the bottomsurface 7 has a round plan shape having the same diameter as the openingand the bottom surface 7 as seen perpendicularly to the outer peripheralsurface 2. That is, the recesses each have a small cylindrical shape.

The depth D of each of the recesses 6 measured along the thickness ofthe elastic member 1 may be set to any value less than the thickness Tof the elastic member 1. The depth D is preferably not less than 50% ofthe thickness T.

If the depth D is less than the aforementioned range, the recesses 6each have a smaller volume, thereby failing to properly function aspockets for trapping paper dust and dirt for a long period of time.

Where the depth D is within the aforementioned range, on the other hand,the recesses 6 can properly function as the pockets for trapping thepaper dust and the dirt for a long period of time.

The upper limit of the depth D may be defined to be less than thethickness T of the elastic member 1. This definition aims to practicallydiscriminate the recesses 6 from the through-holes 8 which each have adepth D equal to the thickness T, and does not mean that the recesses 6and the through-holes 8 have different functions.

The openings of the recesses 6 in the outer peripheral surface 2 of theelastic member 1 may each have an opening diameter Φ arbitrarily set,but the opening diameter Φ is preferably not less than 0.5 mm and notgreater than 5 mm.

If the opening diameter Φ is less than the aforementioned range, therecesses 6 each have a smaller volume, failing to properly function asthe pockets for trapping the paper dust and the dirt for a long periodof time. If the opening diameter Φ is greater than the aforementionedrange, on the other hand, the openings are too large, so that paper dustand dirt once trapped are liable to be released outside the recesses 6.Therefore, the recesses 6 are liable to fail to properly function as thepockets for trapping the paper dust and the dirt for a long period oftime.

In contrast, where the opening diameter Φ is within the aforementionedrange, the recesses 6 can properly function as the pockets for trappingthe paper dust and the dirt for a long period of time.

Referring to FIGS. 1, 3 and 4(a), the through-holes 8 each extend fromthe outer peripheral surface 2 to the inner peripheral surface 3, andeach have an opening having a round plan shape as seen perpendicularlyto the outer peripheral surface 2. A portion of each of thethrough-holes 8 between the outer peripheral surface 2 and the innerperipheral surface 3 has a round plan shape having the same diameter asthe openings of the through-holes 8 in the outer and inner peripheralsurfaces 2, 3 as seen perpendicularly to the outer peripheral surface 2.That is, the through-holes 8 each have a small cylindrical shape.

The openings of the through-holes 8 in the outer peripheral surface 2 ofthe elastic member 1 may each have an opening diameter Φ arbitrarilyset, but the opening diameter Φ is preferably not less than 0.5 mm andnot greater than 5 mm.

If the opening diameter Φ is less than the aforementioned range, thethrough-holes 8 each have a smaller volume, failing to properly functionas the pockets for trapping the paper dust and the dirt for a longperiod of time. If the opening diameter D is greater than theaforementioned range, on the other hand, the openings are too large, sothat paper dust and dirt once trapped are liable to be released outsidethe through-holes 8. Therefore, the through-holes 8 are liable to failto properly function as the pockets for trapping the paper dust and thedirt for a long period of time.

In contrast, where the opening diameter Φ is within the aforementionedrange, the through-holes 8 can properly function as the pockets fortrapping the paper dust and the dirt for a long period of time.

In the illustrated examples, only the plurality of recesses 6 or onlythe plurality of through-holes 8 are provided in the elastic member 1,but the elastic member 1 may include recesses 6 and through-holes 8 incombination.

The plan shape of the opening of each of the recesses 6 or thethrough-holes 8 is not limited to the round shape. FIGS. 4B to 4H areplan views showing other exemplary plan shapes of the opening of therecess 6 or the through-hole 8.

That is, the openings of the recesses 6 or the through-holes 8 may eachhave a given shape inscribed inside a circle C indicated by atwo-dot-and-dash line in FIGS. 4A to 4H, for example, a rectangularshape as shown in FIG. 4B, a rhombic shape as shown in FIG. 4C, apolygonal shape such as a hexagonal shape as shown in FIG. 4D, an ovalshape as shown in FIG. 4E, a V-shape as shown in FIG. 4F, a W-shape asshown in FIG. 4G, or an X-shape as shown in FIG. 4H.

The recesses 6 or the through-holes 8 may each have a plan shape and asize arbitrarily set. In order to facilitate the demolding of avulcanized elastic member 1 from a vulcanization mold in a productionmethod to be described later and to prevent fracture and cracking of theelastic member 1, the recesses 6 preferably each have the same planshape in any portion between the opening in the outer peripheral surface2 and the bottom surface 7. Similarly, the through-holes 8 preferablyeach have the same plan shape in any portion between the opening in theouter peripheral surface 2 and the opening in the inner peripheralsurface 3.

The recesses 6 each having the same plan shape in any portion betweenthe opening in the outer peripheral surface 2 and the bottom surface 7or the through-holes 8 each having the same plan shape in any portionbetween the opening in the outer peripheral surface 2 and the opening inthe inner peripheral surface 3 may be each tapered in a demoldingdirection to facilitate the demolding.

FIG. 5 is a sectional view illustrating an exemplary vulcanization moldto be used for forming the elastic member 1 having the plurality ofrecesses 6 having the openings in the outer peripheral surface 2 in aninventive production method.

Referring to FIGS. 1 and 5, the vulcanization mold 9 includes a pair ofouter molds 11 (upper and lower outer molds 11 in FIG. 5)circumferentially separable from each other and respectively havinginner surfaces which cooperatively define a shape-imparting tubularinner surface 10 corresponding to the outer peripheral surface 2 of theelastic member 1, and an inner mold 13 having a shape-imparting tubularouter surface 12 to be located coaxially with the shape-imparting innersurface 10 of the outer molds 11 about a center axis L2 so as to bespaced a distance corresponding to the thickness T of the elastic member1 from the shape-imparting inner surface 10.

The pair of outer molds 11 each have a plurality of projections 14projecting radially inward from the shape-imparting inner surface 10,and each having a sectional shape corresponding to the plan shape of therecess 6 and a projection height corresponding to the depth D of therecess 6 as measured along the thickness of the elastic member 1.

The projections 14 are arranged on the shape-imparting inner surface 10according to the arrangement of the recesses 6 to be formed in theelastic member 1.

The outer molds 11 are vertically separable from each other with respectto a separation plane 15 extending through the center axis L2 of theshape-imparting tubular inner surface 10.

In the inventive production method, a rubber composition is firstprepared as a material for the elastic member 1. More specifically, atleast one of the rubbers previously described, vulcanization-relatedagents such as a vulcanizing agent, a vulcanization accelerating agentand a vulcanization acceleration assisting agent for vulcanizing therubber, and additives are blended in a predetermined ratio, and theresulting mixture is kneaded to prepare the rubber composition.

Then, the vulcanization mold 9 is preheated to a predeterminedvulcanization temperature, and a space defined between theshape-imparting inner surface 10 of the outer molds 11 and theshape-imparting outer surface 12 of the inner mold 13 of thevulcanization mold 9 disposed coaxially with each other about the centeraxis L2 is filled with a predetermined amount of the rubber composition.

More specifically, the upper and lower outer molds 11 are opened to beeach spaced a greater distance from the inner mold 13 as shown in anupper portion of FIG. 5 and, in this state, the predetermined amount ofthe rubber composition is supplied into the space. At this time, therubber composition may be preheated to a predetermined temperature belowthe vulcanization temperature.

Then, the upper and lower outer molds 11 are closed to be kept in presscontact with each other with a predetermined contact pressure as shownin a lower portion of FIG. 5, so that the outer molds 11 abut againsteach other on the separation plane 15 with the shape-imparting innersurface 10 thereof disposed coaxially with the shape-imparting outersurface 12 of the inner mold 13 about the center axis L2.

In turn, this state is maintained for a predetermined period of time tovulcanize the supplied rubber composition, and then the resultingelastic member 1 is removed by opening the molds. As required, the outerperipheral surface 2 of the elastic member 1 is ground, and the elasticmember 1 is finished to have a predetermined width by cutting axiallyopposite end portions of the elastic member 1.

Then, a sleeve not shown is fitted in the elastic member 1 with an outerperipheral surface thereof fixed to the inner peripheral surface 3 ofthe elastic member 1 directly or with an adhesive agent. Thus, the sheetconveying roller is produced.

According to this production method, the sheet conveying rollerincluding the elastic member 1 having the plurality of recesses 6 can beefficiently produced at higher productivity.

FIG. 6 is a sectional view illustrating an exemplary vulcanization moldto be used for forming the elastic member 1 having the plurality ofthrough-holes 8 having the openings in the outer peripheral surface 2 inanother inventive production method.

Referring to FIGS. 1 and 6, the vulcanization mold 16 includes a pair ofouter molds 18 (upper and lower outer molds 18) circumferentiallyseparable from each other and having inner surfaces cooperativelydefining a shape-imparting tubular inner surface 17 having an innerdiameter equal to a sum of the outer diameter of the elastic member anda predetermined grinding margin, and an inner mold 20 having ashape-imparting tubular outer surface 19 to be located coaxially withthe shape-imparting inner surface 17 about a center axis L3 so as to bespaced a distance equal to a sum of the thickness of the elastic memberand the grinding margin from the shape-imparting inner surface 17.

The inner mold 20 includes a plurality of projections projectingradially outward from the shape-imparting outer surface 19 and eachhaving a sectional shape corresponding to the plan shape of thethrough-hole 8 and a projection height P (T≦P≦G) that is not less thanthe thickness T of the elastic member 1 and less than the sum G of thethickness of the elastic member 1 and the grinding margin.

The projections 21 are arranged on the shape-imparting outer surface 19according to the arrangement of the through-holes 8 to be formed in theelastic member 1.

The outer molds 11 are vertically separable from each other with respectto a separation plane 22 extending through the center axis L3 of theshape-imparting tubular inner surface 17.

In the inventive production method, the vulcanization mold 16 ispreheated to a predetermined vulcanization temperature, and a spacedefined between the shape-imparting inner surface 17 of the outer molds18 and the shape-imparting outer surface 19 of the inner mold 20 of thevulcanization mold 16 disposed coaxially with each other about thecenter axis L3 is filled with a predetermined amount of the rubbercomposition.

More specifically, the upper and lower outer molds 18 are opened to beeach spaced a greater distance from the inner mold 13 as shown in anupper portion of FIG. 6 and, in this state, the predetermined amount ofthe rubber composition is supplied into the space. At this time, therubber composition may be preheated to a predetermined temperature belowthe vulcanization temperature.

Then, the upper and lower outer molds 18 are closed to be kept in presscontact with each other with a predetermined contact pressure as shownin a lower portion of FIG. 6, so that the outer molds 18 abut againsteach other on the separation plane 22 with the shape-imparting innersurface 17 thereof disposed coaxially with the shape-imparting outersurface 19 of the inner mold 20 about the center axis L3.

In turn, this state is maintained for a predetermined period of time tovulcanize the supplied rubber composition, and then the resultingelastic body is removed by opening the molds.

In this state, a rubber layer having a thickness corresponding to thegrinding margin is present in an outer peripheral portion of the elasticbody, so that the recesses formed as corresponding to the projections 21are not open in the outer peripheral surface 2. Therefore, the outerperipheral portion is ground by the grinding margin, whereby therecesses are open in the outer peripheral surface 2 to form thethrough-holes 8.

Then, the resulting elastic member 1 is finished to have a predeterminedwidth by cutting axially opposite end portions of the elastic member 1.Then, a sleeve not shown is fitted in the elastic member 1 with an outerperipheral surface thereof fixed to the inner peripheral surface 3 ofthe elastic member 1 directly or with an adhesive agent. Thus, the sheetconveying roller is produced.

According to this production method, the sheet conveying rollerincluding the elastic member 1 having the plurality of through-holes 8can be efficiently produced at higher productivity.

The present invention is not limited to the embodiments described abovewith reference to the drawings.

For example, the recesses 6 or the through-holes 8 are merely requiredto be equidistantly arranged in the center axis L1 direction of theelastic member 1 and equidistantly arranged in the circumferentialdirection of the elastic member 1, but the arrangement of the recesses 6or the through-holes 8 is not limited to that shown in FIG. 1.

Further, all the openings of the recesses 6 or the through-holes 8 arenot required to have the same round shape as shown in FIG. 1, butopenings of the recesses 6 or the through-holes 8 having two or moredifferent plan shapes may be present in combination in the outerperipheral surface 2. In this case, the openings of the recesses 6 orthe through-holes 8 having different plan shapes preferably have thesame opening area in order to ensure that the recesses 6 or thethrough-holes 8 can efficiently and evenly function as the pockets fortrapping the paper dust and the dirt on the entire outer peripheralsurface 2.

It should be understood that various modifications may be made withoutdeparting from the scope of the present invention.

EXAMPLES

An elastic member 1 having a three-dimensional shape as shown in FIG. 1,an outer diameter of 24.6 mm and a width of 28.5 mm as measured in acenter axis L1 direction thereof and including a plurality ofthrough-holes 8 each having a round plan shape as seen perpendicularlyto the outer peripheral surface 2 and arranged in an arrangement asshown in FIG. 1 was produced by the vulcanization utilizing the mold 16shown in FIG. 6, the grinding of the grinding margin for the exposure ofthe through-holes 8, and the cutting of the opposite end portionsthereof. A mold temperature of 160° C. to 170° C. and a vulcanizationperiod of 20 minutes were employed for vulcanization conditions.

Such elastic members 1 were produced with the outer diameter, the numberand the interval of the projections 21 for the through-holes 8 changedto change the opening diameter Φ and the number of the through-holes 8aligned in each line extending in the center axis L1 direction (in aline containing through-holes greater in number by one) as shown belowin Table 1. The number of the through-holes 8 aligned in each line wasset so that the product (Φ×N) of the opening diameter Φ and the number Nwas substantially constant as shown below in Table 1.

A sleeve not shown was fitted in each of the elastic members 1 with anouter peripheral surface thereof fixed to the inner peripheral surface 3of the elastic member 1 with an adhesive agent. Thus, sheet conveyingrollers were produced, which were compatible with a laser printer HPLaserJet (registered trade name) P4515n available from Japan HewlettPackard Company.

For comparison, an elastic member having the same dimensions as theelastic members 1 but having no through-holes was formed, and a sheetconveying roller was produced by using the elastic member thus formed.

The sheet conveying rollers thus produced were each brought into presscontact with a paper sheet (Xerox Business 4200 available from XeroxCorporation and having a width of 60 mm and a length of 210 mm) placedon a TEFLON (registered trade name) plate with a vertical load of 340 gfand, in this state, a transportation force F acting on the paper sheetwas measured by means of a load cell while the sheet conveying rollerwas rotated at a circumferential speed of 105 mm/sec. Then, a frictioncoefficient μ was determined from the following expression (4):

μ=F/340  (4)

Measurement was performed immediately after the production of each ofthe sheet conveying rollers (initial measurement) and after 10000 papersheets (available under the trade name of SILVER STAR from Silver StarPaper Corporation in China) were passed over each of the sheet conveyingrollers incorporated as a sheet feed roller in the laser printer(post-endurance measurement).

The results are shown in Table 1.

TABLE 1 Through-holes 8 Friction coefficient μ Opening Number N of Post-diameter Φ through-holes Initial endurance (mm) in each line Φ × Nmeasurement measurement 0.4 42 16.8 2.05 1.0 0.5 34 17 2.0 1.7 1 17 171.9 1.6 5 3 15 1.9 1.7 6 2 12 1.7 0.9 7 2 14 1.7 1.0 No through-holes2.05 0.9

Table 1 indicates that the opening diameter Φ of the through-holes 8 asmeasured on the outer peripheral surface 2 of the elastic member 1 ispreferably not less than 0.5 mm and not greater than 5 mm in order topermit the through-holes 8 to properly function as pockets for trappingpaper dust and dirt.

Further, it was found that, where the through-holes 8 are providedequidistantly in the center axis L1 direction of the outer peripheralsurface 2, the through-holes 8 occupy an area of 50% to 60% of the outerperipheral surface 2 as measured in the center axis L1 direction.

This application corresponds to Japanese Patent Application No.2012-031793 filed in the Japan Patent Office on Feb. 16, 2012, thedisclosure of which is incorporated herein by reference in its entirety.

DESCRIPTION OF REFERENCE CHARACTERS

-   -   1 ELASTIC MEMBER    -   2 OUTER PERIPHERAL SURFACE    -   3 INNER PERIPHERAL SURFACE    -   4,5 END FACES    -   6 RECESSES    -   7 BOTTOM SURFACES    -   8 THROUGH-HOLES    -   9 VULCANIZATION MOLD    -   10 SHAPE-IMPARTING INNER SURFACE    -   11 OUTER MOLDS    -   12 SHAPE-IMPARTING OUTER SURFACE    -   13 INNER MOLD    -   14 PROJECTIONS    -   15 SEPARATION PLANE    -   16 VULCANIZATION MOLD    -   17 SHAPE-IMPARTING INNER SURFACE    -   18 OUTER MOLDS    -   19 SHAPE-IMPARTING OUTER SURFACE    -   20 INNER MOLD    -   21 PROJECTIONS    -   22 SEPARATION PLANE

What is claimed is:
 1. A sheet conveying roller comprising: a non-poroustubular elastic member; wherein the elastic member has a plurality ofrecesses provided in an outer peripheral surface thereof asequidistantly arranged in a center axis direction thereof andequidistantly arranged in a circumferential direction thereof, therecesses each having an opening having a round plan shape as seenperpendicularly to the outer peripheral surface in the outer peripheralsurface, and each having a predetermined depth as measured thicknesswiseof the elastic member.
 2. The sheet conveying roller according to claim1, wherein the recesses include cylindrical recesses.
 3. The sheetconveying roller according to claim 2, wherein the recesses each have anopening diameter of 0.5 mm to 5 mm.
 4. The sheet conveying rolleraccording to claim 3, wherein the recesses are equidistantly arranged inthe center axis direction of the elastic member so as to occupy an areaof 50% to 60% of the outer peripheral surface of the elastic member asmeasured in the center axis direction of the elastic member.
 5. Thesheet conveying roller according to claim 1, wherein the recessesinclude columnar recesses each having a polygonal plan shape, an ovalplan shape or any other plan shape inscribed inside the round plan shapeas seen perpendicularly to the outer peripheral surface.
 6. A sheetconveying roller comprising: a non-porous tubular elastic member havingan outer peripheral surface and an inner peripheral surface disposedcoaxially with each other; wherein the elastic member has a plurality ofthrough-holes equidistantly arranged in a center axis direction thereofand equidistantly arranged in a circumferential direction thereof, thethrough-holes each having an opening having a round plan shape as seenperpendicularly to the outer peripheral surface in the outer peripheralsurface and extending thicknesswise through the elastic member to theinner peripheral surface.
 7. The sheet conveying roller according toclaim 6, wherein the through-holes include cylindrical through-holes. 8.The sheet conveying roller according to claim 7, wherein thethrough-holes each have an opening diameter of 0.5 mm to 5 mm.
 9. Thesheet conveying roller according to claim 8, wherein the through-holesare arranged in the center axis direction of the elastic member so as tooccupy an area of 50% to 60% of the outer peripheral surface of theelastic member as measured in the center axis direction of the elasticmember.
 10. The sheet conveying roller according to claim 6, wherein thethrough-holes include columnar through-holes each having a polygonalplan shape, an oval plan shape or any other plan shape inscribed insidethe round plan shape as seen perpendicularly to the outer peripheralsurface.
 11. A method of producing a sheet conveying roller including anonporous tubular elastic member having a plurality of columnar recessesin an outer peripheral surface thereof, the method comprising the stepsof: providing a vulcanization mold which includes an outer mold and aninner mold, the outer mold being circumferentially dividable into atleast two mold pieces, and having a shape-imparting tubular innersurface corresponding to the outer peripheral surface of the elasticmember, and a plurality of projections projecting radially inward fromthe shape-imparting inner surface and each having a sectional shapecorresponding to a plan shape of the columnar recesses of the elasticmember and a projection height corresponding to a depth of the columnarrecesses as measured thicknesswise of the elastic member, the inner moldhaving a shape-imparting tubular outer surface to be located coaxiallywith the shape-imparting inner surface so as to be spaced a distancecorresponding to a thickness of the elastic member from theshape-imparting inner surface; and forming the nonporous tubular elasticmember with the plurality of recesses formed as corresponding to theprojections in the outer peripheral surface thereof by preheating thevulcanization mold, locating the shape-imparting inner surface of theouter mold and the shape-imparting outer surface of the inner mold ofthe vulcanization mold coaxially with each other, filling a spacedefined between the shape-imparting inner surface and theshape-imparting outer surface with a rubber composition as a materialfor the elastic member, and vulcanizing the rubber composition.
 12. Amethod of producing a sheet conveying roller including a nonporoustubular elastic member having a plurality of columnar through-holesextending through the elastic member, the method comprising the stepsof: (1) providing a vulcanization mold which includes an outer mold andan inner mold, the outer mold being circumferentially dividable into atleast two mold pieces, and having a shape-imparting tubular innersurface having an inner diameter equal to a sum of an outer diameter ofthe tubular elastic member and a predetermined grinding margin, theinner mold having a shape-imparting tubular outer surface to be locatedcoaxially with the shape-imparting inner surface so as to be spaced adistance equal to a sum of a thickness of the elastic member and thegrinding margin from the shape-imparting inner surface, and a pluralityof projections projecting radially outward from the shape-impartingouter surface and each having a sectional shape corresponding to a planshape of the columnar through-holes of the elastic member and aprojection height that is not less than the thickness of the elasticmember and less than the sum of the thickness of the elastic member andthe grinding margin, and forming a nonporous tubular elastic body havinga plurality of columnar recesses corresponding to the projections in aninner peripheral surface of the elastic body by preheating thevulcanization mold, locating the shape-imparting inner surface of theouter mold and the shape-imparting outer surface of the inner mold ofthe vulcanization mold coaxially with each other, filling a spacedefined between the shape-imparting inner surface and theshape-imparting outer surface with a rubber composition as a materialfor the elastic member, and vulcanizing the rubber composition; and (2)grinding an outer peripheral portion of the elastic body by the grindingmargin to expose the columnar recesses in an outer peripheral surface ofthe resulting elastic body to form the plurality of through-holes in theelastic member.